DE3123325A1 - FUEL INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES - Google Patents

Description

ε. 707 2

Bö / Jä 11.5.1981

Robert Bosch GmbH, TOOO Stuttgart 1

State of the art fuel injection device for internal combustion engines

The invention is based on a fuel injection device according to the genre of the main claim. In such an injection device known from DE-OS 19 19 969 the amount of fuel injected during the delivery stroke of the pump piston of an injection pump should be - by a solenoid valve, which is clocked or controlled in an analogue manner, on the exhaust stroke of the Pump piston metered. The metered quantity is determined by the opening time of the solenoid valve, with the opening phase of this valve exclusively is in the suction stroke range of the pump piston. In this known device, the pressure conditions influence the metered quantity in the working chamber and the valve cross-section of the fuel injection pump. For an accurate Need to meter the amount of fuel injected in this known device for measuring the opening times of the solenoid valve, the speed and the Injection time must be taken into account. There are still the pressure fluctuations in the work area during to be observed during the filling process. Further disadvantages result from the limited switching speed a solenoid valve. The during the proportioning phase at

Suction stroke takes place two switching operations of the solenoid valve "thus influence the accuracy of the metering result Furthermore, the speed ″ or the injection pump speed Limits are set by the switching time of the solenoid valve,

In another by the DE-OS 19 19 707 "known Kraf tst of f exinsprit zpump was taken into account for the "limited switching speed of solenoid valves" worn that "with this distributor pump in the distributor two pump systems are housed, each of which is supplied with fuel via a solenoid valve. In this way, a higher pump speed can be achieved. Furthermore, this injection pump the cam drive of the pump piston designed so that the stroke speed of the pump piston during the suction stroke is significantly less than that of the pump piston during the delivery stroke. The solenoid valve of each pump system of this radial piston pump is also exclusively during the suction stroke the pump piston opens, the opening duration of the solenoid valve determines the metered quantity. Here too, the speed and injection timing must be adjusted must be taken into account when controlling the solenoid valves. When designing this pump, the begins Timing of the solenoid valve with the suction stroke of the associated pump piston. A start of injection adjustment is required a change in the start of the suction stroke, so that this suction stroke starts exactly when calculating the opening time of the solenoid valve must be entered. There are also the dynamic conditions at the turning point of the pump piston at the transition from the delivery stroke to the suction stroke is difficult to control. Because of the duplicate

The pump system in this fuel injection pump is the Setup continues to be very complex.

Advantages of the invention

The fuel injection device according to the invention with the characterizing features of the main claim has the advantage that the funding phase, a flushing phase follows the period in which fuel is delivered into the injection lines. In this flushing phase, which also includes the remaining pressure stroke of the pump piston, the pump work space becomes the fuel injection pump via the electrically operated valve and possibly via the relief line, if this to the pump suction chamber that is usually present in a fuel injection pump leads, constantly filled with fuel, which is below that in the pump suction chamber or in the fuel supply source pending delivery pressure. At the time of closing the relief channel prevail thus balanced pressure conditions, so that with a sufficiently large metering cross-section at the valve, the opening time of the valve related to the speed or the opening phase over a certain suction stroke length of the Pump piston an exact measure for the injection quantity is. Since during the flushing time, for. B. following the delivery stroke of the pump piston, the electrically actuated Metering valve is already open, determines in an advantageous manner the closing time of the relief channel the start of metering through the control edge. This closing takes place without the time taken into account for the solenoid valve loss, so that the metered quantity is only influenced by the closing time of the valve at the end of the metering phase can be.

Through the measures listed in the subclaims' advantageous developments and improvements of the solution specified in the main claim are characterized.

drawing

An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. 1 shows the exemplary embodiment in a basic representation, FIG. 2a shows a diagram of the switching time of the metering valve over the angle of rotation, FIG. 2b shows the stroke curve of the pump piston in association with the switching times of the metering valve, FIG. with a measuring device for recording the control times of the relief channel, FIG. k shows an enlarged representation of the device for recording the switching times of the relief channel, FIG. 5 shows a first modified form of the device according to FIG. k, FIG. 6 shows a second modified form of the device according to FIG k., Fig. 7 a device for detecting the lifting movement of the pump piston, Fig. 8 shows a modification of the embodiment of Fig. 1 with a modified injection timing adjusting device, Fig. 9 shows a further development of the embodiment with the supply of several cylinders by a solenoid valve.

Description of the embodiment

In the exemplary embodiment shown in FIG. 1, a bore 2 is provided in a pump housing 1, in which a pump piston 3 encloses a pump working space h . The pump piston is driven by a cam disk 5 that runs on a roller ring 6

The fuel is supplied to the pump working chamber via a fuel inlet channel 8 which leads from a pump suction chamber 9 a fuel feed pump 11 is supplied with fuel from a fuel tank 12, the pressure in the pump suction chamber 9 being set with the aid of a pressure control valve 1 h which is connected in parallel with the fuel feed pump 11.

In the fuel inlet duct is an electrically operated valve 16 which, for. B. can be a solenoid valve, used as a fuel metering device. Downstream of this valve there is also provided a check valve 17 which opens in the direction of the fuel inflow into the pump working chamber k. A blind bore 18 arranged in the pump piston 3 leads from the pump working space h, from the end of which a radial bore 19 leads to the outside. A further radial bore 20 connects the blind bore 18 with a distributor groove 21 through which conveying lines 22 are successively connected to the pump working chamber k when the pump piston rotates and its conveying stroke. The delivery lines are distributed around the circumference of the bore 2 in accordance with the number of cylinders of the associated internal combustion engine to be supplied and each contain a relief valve 23 and are each connected to an injection valve 2k . In the wall of the bore 2, an annular groove 26 is also provided, which is connected to the pump suction chamber 9 via at least one bore 27. The annular groove 26 is arranged so that the radial bore 19

opened in the pump piston 2 from a maximum delivery stroke is, so that the promoted from this point in the further stroke movement of the pump piston 2 Fuel via the blind hole 18 serving as a relief channel, the radial hole 19 and the hole 27 can flow off into the suction chamber 9 and thus interrupted the pressure delivery into the delivery line 22 will.

To change the injection time, an injection adjustment piston 29 is also provided, which is connected to. is coupled to the cam ring 5 and is adjustable against the force of a spring 30. The injection adjustment piston includes a pressure chamber 31 which is connected to the pump suction chamber via a throttle 32 and is thus acted upon by the speed-dependent pressure in the pump suction chamber. Corresponding to this speed-dependent pressure, the injection timing point is adjusted to early with the aid of the injection adjuster piston by turning the cam ring with increasing speed. To influence the injection timing, the pressure chamber 31 is also connected ^{to the suction side of the feed pump 11 via a solenoid valve 3 1} J-, and the pressure can be relieved with the aid of this valve. The solenoid valve 3 ^ is controlled by a control unit 36, which also serves to control the electrically operated valve 16 in the fuel inlet channel. To this end, the control unit works as a function of parameters that must be taken into account for the measurement and timing of the fuel injection quantity. The control unit can, for. B. contain at least one map in which setpoints for the amount of fuel to be injected in direct or indirect form

are included. In a manner known per se, the speed, the temperature, the air pressure and the load can be taken into account as parameters. Signals from a needle lift sensor in injection valve 2k for determining the actual start of injection and the actual fuel injection duration can be detected as additional parameters specifically for the activation of the solenoid valve. As an alternative to this, control signals can also be used via a pressure transmitter 38, which is arranged in a suitable manner on the high-pressure side of the fuel injection pump, to determine the start of delivery or the duration of delivery. To determine the stroke position of the pump piston and / or its speed, a transmitter 39 z. B. be provided in the form of an inductive sensor on the cam 5.

The mode of operation of the fuel injection device shown in FIG. 1 will now be explained with the aid of the diagrams in FIGS. 2a and 2b. Fig. 2b shows the elevation curve of the pump piston over the angle of rotation ^. By appropriate design of the cam disk 5 it has been achieved that the change in stroke per angle of rotation ^ during the pressure or delivery stroke of the pump piston is significantly greater than the change in stroke during the suction stroke of the pump piston. This curve part B of the elevation curve is very flat and linear except for the limit area at the reversal points of the pump piston. The pressure stroke part A of the curve in FIG. 2b is divided into three route sections. Between the bottom dead center UT of the pump piston at the beginning of the pressure stroke up to the point FB, the fuel present in the pump working space k is compressed until the delivery pressure is sufficient to open the

707

Nozzle 2 \ causes is reached. The second part of the curve now extends between FB and EO. In this area, fuel is delivered into the delivery channel 22. As a result of the delivery pressure, the check valve 1Tj continues to be closed, possibly supported by the spring installed there. The electrically actuatable valve 16, which is here e.g. B. is designed as a slide valve, depressurized.

When the point EO of the elevation curve is reached, the radial bore 19 is brought into connection with the annular groove, so that the pressure chamber h is relieved into the suction chamber 9. The remaining amount of fuel displaced by the pump piston flows there. This takes place in the area between the opening of the relief channel (EO) and top dead center (OT). At the latest when reaching the point OT. the solenoid valve 16 is opened. The opening can take place earlier, since the fuel inlet channel 8 is closed by the check valve 17 during the pressure stroke. In the area between TDC and the closing point of the relief channel ES, fuel is now sucked in via the large opening cross section of the valve 16. The pressure equalization in the pump working space can also take place via the relief channel 18, the radial bore 19 and the bore 27. In the area between EO and ES it is ensured that the pressure in the working space k is balanced and the working space -h is constantly filled and flushed. The effective suction stroke of the pump piston begins from ES. Until the solenoid valve closes at MS, fuel is sucked in. The effective suction stroke length 0 (.T is thus determined on the one hand by the geometric design of the fuel injection pump or by the

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Position of the control edge delimiting the annular groove 26 and on the other hand by the switching time of the solenoid valve. In Fig. 2a, the switching times of the solenoid valve are recorded, where <X. 1 is the total opening time of the solenoid valve and {jL_ 2 is the time effective for metering designated.

Since the solenoid valve can be opened much earlier than the actual effective suction stroke begins and there is still one between the effective delivery stroke and the effective suction stroke of the pump piston The flushing phase (EO-ES) needs the injection time to be within the possible range when the solenoid valve is opened Injection timing adjustment range not taken into account will. The fuel metering control influences or hinders the injection timing adjustment options not. The flat cam profile during the suction stroke also has the advantage that the Pump piston can constantly follow crouching even at high speed without the pump piston jumping off occurs within the effective suction stroke and thus affects the amount of fuel sucked in .

The Uocken slope becomes advantageous over the possible The length of the effective suction stroke is linear, which is particularly advantageous for corrective interventions affects. In principle, however, the type of metering does not depend on the linearity of the collection curve dependent, but facilitates precise metering. By defining the effective suction stroke length you get a very good metering accuracy of the amount of fuel to be metered. In the simplest case it can

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the effective suction stroke length for direct metering -be controlled without feedback of the actual amount of fuel injected required ■ would be. You get very good tax results if the actual fuel injection quantity by means of the control unit is detected in a manner known per se and in a comparison device of the control unit a target fuel quantity signal formed there is compared. The actual amount of fuel can be As mentioned at the beginning, by a needle stroke transmitter or by a correspondingly evaluated pressure signal of the pressure transducer 38 can be determined. The target amount of fuel is derived from the parameters mentioned at the beginning formed with the load as a reference variable. The actual opening time is then corresponding to the result of the comparison of the solenoid valve if the actual fuel quantity deviates from the nominal value corrected. The basic opening signal of the valve 16 is according to the target fuel amount signal educated.

For the exact detection of the elevation point at which the relief channel 19 is closed again (ES), a transmitter UO is advantageously provided, as shown in FIG. 3. Incidentally, the fuel injection device according corresponds to Fig. 3 to Fig. 1. In Fig. K such a donor is drawn out is greater. The bore 27 'in this further development of the fuel injection device also leads from the annular groove 26 and via the sender ¹ JO with complete pressure relief to the suction side of the fuel feed pump 11 or to the fuel reservoir 12. The sender Uo is thus located in a pressure-relieved space i; 1. The exit of the hole 27 '

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into the pressure-relieved space h '] is controlled by a valve closing part U3, which is attached to a leaf spring h-5. This is attached at the other end via an insulating piece k6 on the pump housing, which at the same time represents the ground connection. An electrical line 2 leads from the leaf spring, which in another embodiment can also be a membrane or spider in a suitable configuration, to the control unit 36. Furthermore, a throttle bore lj-8 is provided coaxially to the axis of the bore 27 'in the valve closing part, via which the bore 27 'is constantly connected to the space Ui even when the valve closure member U3 is in the closed position. A pressure can build up in the bore 27 ′ at this throttle bore as long as fuel continues to flow from the pump working space h via the blind bore 18. This is the case as long as the radial bore 19 is in connection with the annular groove 26 and as long as the solenoid valve 16 is open. This condition is given for the range of suction stroke B between OT and ES. Under the resulting pressure, the valve closing part ^ 3 lifts from its seat on the bore 27 'and thus interrupts the circuit to the ground. However, as soon as the connection between the radial bore 19 and the bore 27 'is interrupted again in the course of the suction stroke of the pump piston, the valve closing part k3 returns to its seat and closes the circuit. This is the signal that the effective suction stroke has started. The signal is processed accordingly in the control unit 36, which can advantageously take place with the aid of an integrating device.

IO 70

The integrating means is gesetzt- with the closing signal of the Geyer 1 h and when the output value of the integrator has reached the given from the control unit 36 set value for the amount of fuel discharged from a comparison device of the two values a switching signal to the solenoid valve for closing the fuel inlet channel. So that the switching time of the valve 16 is purely related to the stroke length, the running time of the integrator must be corrected during the integration by an integration time constant adapted to the speed. This can be done with known methods, on the one hand, by making the design of the integrator itself speed-dependent in an analog manner. Or by integrating the integrator in constant integration steps with speed-dependent frequency.

In another embodiment, a TDC signal, which is achieved with the aid of the transmitter 39 and the closing signal · · given by the transmitter If-O Correction signal can be generated that the opening phase of the speed-synchronized valve corrected.

The design of the transmitter Uo according to FIGS. 3 and h also allows the formation of an opening signal for opening the bore 27 '. With this opening signal, an opening signal for the valve 16 could be formed, for example.

In Fig. 5 is an alternative embodiment of the Encoder for opening or closing the bore 27 'is shown. The in Fig. If- in the closing part U 3 provided throttle bore If-8 is in this one

Design in a branch duct \ 9 ', which leads to the pressure-relieved space kl , provided as a throttle 50. In the embodiment according to FIG. 6, a throttle 51 is provided at the outlet of the bore 27 'into the pressure-relieved space U1 and a pressure transducer 52 is arranged upstream of this throttle 51 in the wall of the bore 27'. The pressure signal emitted by this is preferably converted into the closing signal or the opening signal via a threshold switch.

Instead of the speed-compensated integration described above, it is also possible to use the pump piston a lift sensor 5 ^ to be assigned, which is shown in FIG is. For this purpose, with the pump piston 3, a pulse generator 55 is parallel to the pump piston axis provided to which a transducer, e.g. B. an inductive pickup 56 is assigned. The impulse generator can z. B. consist of magnetized parts lying one behind the other or designed as a toothed strip be. Such pulse generators are known in principle and do not need to be described in more detail here. the Signals emitted by the encoder 56 are then integrated in an integrator, the speed or the stroke speed of the pump piston no longer needs to be taken into account.

The fuel injection device in the above-described designs of the fuel and their developments The related principle can also be applied to a fuel injection pump, which is shown in of the type in-line pump. Fig. 8 shows a pump piston 6θ as one of the pump pistons of the

-J ⁴ - 70

In-line pump. This pump piston can be moved up and down in a cylinder 61 for the purpose of suction and fuel delivery and can also be rotated at the same time. It encloses a pump working chamber 62 in the pump cylinder, from which a fuel injection nozzle is supplied with fuel. A fuel inlet channel 8 ′, which, as in FIG. 1, contains a check valve 17 ′ and an electrically actuatable metering valve 16 also opens into the working space 62. To achieve a flushing phase as described above, the pump piston has an inclined control edge 63 which delimits a partial annular groove 6k in the lateral surface of the pump piston. The partial annular groove is connected to the pump working chamber 62 via a longitudinal groove 65 or via a corresponding bore. The oblique control edge works with a discharge channel ^{27! L} together, the displaced fuel can flow from the working chamber 62 through the remaining stroke of the pump piston during a 60th Depending on the rotational position of the pump piston, set by z. B. by a rack 70, the relief channel 27 'is opened sooner or later or closed again. As a result of the rotary position of the piston, an injection adjustment, ie a variable end of delivery, can be achieved. To detect the start of the effective suction stroke, the rotational position of the pump piston 60 z. B. on the rack 70 detecting sensor 71 can be used, whose correction signal is taken into account by a corresponding control unit in the formation of the opening pulse of the electrically operated valve,

As FIG. 9 shows, it is possible to use an electrically operated metering valve to have several pump pistons

to provide fuel. Every single pump basket is thereby "advantageously a check valve 67, 68 assigned. A condition for such a configuration is that the cam trailing edge, i.e. the stroke of the pump piston during the effective suction stroke "is the same for both pistons.

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Claims (1)

R. Bö / Jä 11.5.1981 Robert, Bcrsch GmbH, 7000 Stuttgart 1 Expectations 1./Fuel injection device with at least one working chamber enclosed by a pump piston in a cylinder, which can be connected to the fuel injection point via at least one delivery line and, during the suction stroke, with a fuel quantity metering device that can be electrically operated by a control unit and to a fuel supply source leading fuel inlet channel can be connected, characterized in that a relief channel (18, 19, 27; 65, 6k-, 27 '') leads from the pump part (h, 62) , the passage cross-section of which is guided by a synchronous to the movement of the pump piston Control edge (26, 63) is controllable on a once rapid pressure stroke of the pump piston and from a suction stroke corresponding to the remaining stroke of the pump piston can be closed again and that the fuel quantity metering device (16) as an electrically operated valve is designed, which can be brought into an open position or a closed position depending on the control and can be switched by the control unit (36) in such a way that it is already activated before the relief channel is closed is open and, depending on the size of the amount of fuel to be injected, sooner or later after closing of the relief channel is closed during the suction stroke of the pump piston (2). 2. Fuel injection device according to claim 1, characterized in that the pump piston (2, 6o) is periodically actuated by a cam track (.5) is designed so that the stroke change of the pump piston per unit of movement of the cam during the suction stroke of the pump piston is significantly less than during the pressure stroke of the Pump piston. 3. Fuel injection device according to claim 2, characterized in that the cam is designed so that the stroke change of the pump piston per unit of movement (angle of rotation) of the cam track in the area of the effective suction stroke of the pump piston is constant. It · -. Fuel injection device -according to one of claims-1 "to 3 j characterized; that to control the Fuel quantity is the effective suction stroke length after closing of the relief duct by the valve's opening time, is controllable. 5. Fuel injection device according to claim h, characterized in that the control unit (36) is connected to a transmitter (2 ^, 38) for the actual fuel injection quantity, the output / value of which is compared in a comparison device in the control unit with the target fuel quantity signal , a correction signal for an opening duration signal of the valve formed in accordance with the setpoint value being formed in accordance with the output signal of the comparison device. 6. Fuel injection device according to claim 5, characterized in that the control unit is connected to a transmitter (Uo) that controls the closing of the Relief channel emits detecting signal and that a correction signal corresponding to the closing signal can be generated, according to which the position of the opening phase of the valve (16) can be changed. j U M ί Χ » 7. Fuel injection device according to claim 5, characterized in that as an actual fuel injection quantity sender a pressure transducer (38) which detects the delivery phase is provided. 8. Fuel injection device according to claim 5, characterized in that the actual fuel quantity transmitter is provided as a transmitter which detects the Uadelhub of the injection nozzle (2k). 9. Fuel injection device according to claim k, characterized in that the control unit (36) is connected to a transmitter (Uo) which emits a signal indicative of the closing of the relief duct or the beginning of the effective suction stroke length, by means of which an opening signal for determining the effective suction stroke length the valve is set, the length of the opening duration signal corresponding to the respective target value of the fuel metered quantity. 10. Fuel injection device according to claim 9, characterized in that an integrator can be set by the closing signal, the integration value of which with a setpoint value in a comparison device im - 5 - Wed / Control unit is compared and that the comparison device when the setpoint is reached, a switching signal can be sent to the valve. 11. Fuel injection device according to claim 10, characterized in that the integration constancy of the integrator depends on the speed. 12. Fuel injection device according to claim 11, characterized in that the integrator has constant integration.s. steps in the speed-dependent cycle added. 13. Fuel injection device according to claim k, characterized in that the control unit is connected to a stroke length transmitter (5k) to form the signal controlling the valve. Ik. Fuel injection device according to Claim 13, characterized in that the stroke length transmitter generates equidistant pulses along the stroke of the pump piston and is connected to an integrator which can be set by a closing signal of the relief duct and whose integration value is in a ver— 7072 equalization device of the control device is compared with a setpoint value, when the setpoint value is reached a switching signal for the valve (16) is generated. 15 · Fuel injection device according to one of Claims 6 to 1 ^, characterized in that a throttle (U8, 50, 51) is arranged downstream of the control edge (26) in the relief channel (27 '') leading to a space (Ui) with low pressure and a pressure transducer (^ 5, h3; 52) is provided which is exposed to the pressure in the relief line (27 ¹ ) upstream of the throttle point and that a signal for the open state and the closed state of the relief channel can be formed from the output signal of the pressure transducer. 16. Fuel injection device according to claim 15 , characterized in that the pressure transducer consists of a spring (^ 5) which is electrically isolated from its fastening parts and has a closing member (^ 3) designed as a closing member of the relief line (27 '), which through the bias of the spring can be pressed against the outlet opening of the relief line. 3Ί23325 70 7 ι 17 · Fuel injection device according to claim 16, characterized in that in the overlap area of the closing part (^ 3) with the outlet opening of the Relief line (27 ') the throttle is arranged as a through hole (U8) through the closing part (^ 3). 18. Fuel injection device after one of the gate stands Claims, characterized in that a device for adjusting the injection timing the rotary position of the pump piston is provided relative to the pump piston drive. 19. Fuel injection device according to one of the preceding Claims 1 to 18, characterized in that the control edge (63) runs obliquely and for adjusting the injection time the control edge is adjustable transversely. 20. Fuel injection device according to claim 19 »thereby characterized that with an adjusting device (TO) for the rotary position of the control edge a position . encoder (71) is connected, through which a signal for the Detection of the effective start of suction can be derived. 21. Fuel injection device according to one of the preceding Claims, characterized in that between the electrically operated valve (16) in the fuel inlet duct (8) and the working space -der Fuel injection pump arranged a check valve that opens in the direction of the workspace. 22. Fuel injection device according to claim 21, characterized in that the valve closing member of the electrically "actuatable valve when de-energized The valve can be held in the closed position by the delivery pressure in the working chamber of the fuel injection pump is.